let str = 'aabbccc';

let arr = {}

arr = str.split('').reduce((arr, item) => {
    // console.log(item);
    // console.log(arr);
    if (arr.hasOwnProperty(item)) {
        arr[item]++
    } else {
        arr[item] = 1
    }
    return arr

}, {})

console.log(arr)


var arr1 = new Array("1", "2", "3");
var arr2 = new Array("4", "5", "6");
arr1.push.apply(arr1, arr2)
console.log(arr1);

